In the production of lumber products (e.g., boards, posts, etc.) the wood is dried prior to being planed. Typically, the lumber is stacked on rail cars or other carriages and moved into a kiln for batch drying of the wood. The kiln is heated by a burner to dry the wood over a set period of time. The moisture driven out of the wood is drained from the kiln and discharged into the environment.
The effluent produced during the drying process or during cleaning of the kilns creates a potential environmental hazard when discharged into rivers, lakes or other natural surroundings. States have therefore begun to ban or consider banning the discharge of water from the operation of kilns into the environment. As a result, wood drying facilities are faced with the prospect of shutting down for lack of a solution to the problem of disposing of kiln water.
Wood drying plants have also generally suffered from an inability to provide uniformly dried products ready for planing or other processing. In particular, the moisture content in the individual lumber products is not uniform. Consequently, the time needed to dry each individual piece of wood varies from piece to piece. Nevertheless, for production purposes, the entire stack of wood is heated for a single predetermined time. As a result, some of the wood becomes over dry and suffers from cracking, warping, etc.
The burners of a direct fired kiln or the like are generally fueled, at least in part, by the shavings or other offal produced by planing or other processing of the wood. Using the wood shavings as fuel provides an efficient, cost-effective management of the resources involved in the operation and solves a solid waste disposal problem. However, significant levels of fly ash generated in the burners is blown into the kilns. The ash, in turn, settles on the wood and in the water being driven out of the wood. As can be appreciated, the ash degrades the quality of the lumber, which can require an increase in the planing operation or a reduction in the final value of the product.